White's plan is to open the bishop's diagonal and fix the structure on the queenside with b4-b5.
5... e8d6  6. e1d3  6... h7h5 Before developing the knight, Sindarov decides to improve the structure on the kingside, avoiding being stuck with a fixed pawn on h7. He could also choose 6...h6. 7. d3e5  7... g8e7 